I. Field
The present invention relates generally to wireless communication and, more particularly, to an apparatus and method for filtering baseband signals in a wireless communication system.
II. Related Art
Wireless communication systems have increased in number and complexity in recent years. It is common for a plurality of wireless service providers to operate in the same geographic region with overlapping areas of coverage. Because of the increased number of wireless service providers and increased usage, portions of the frequency spectrum allocated to wireless service are often utilized to their capacity or beyond.
A code division multiple access (CDMA) wireless system has a significant capacity because multiple users can simultaneously communicate on the same radio frequency (RF) channel by digitally encoding each transmission using channelization codes. An RF channel refers to a portion of the frequency spectrum. The channelization codes, which are sometimes referred to as orthogonal codes, encode the transmission for each wireless communication device so that a transmission for a given wireless communication device can be recovered by that device while the same transmission appears as noise to other wireless communication devices. Thus, a CDMA system allows multiple users to operate simultaneously on the same RF channel.
Within a particular geographical locale, multiple base transceiver systems (BTSs) may operate on different RF channels so as to minimize interference with adjacent areas of coverage. In many wireless communication systems, there is a guard band or portion of the frequency spectrum separating the RF channels to provide further protection against interference between BTSs.
However, some wireless communication systems do not have an adequate guard band or have no guard band at all. This operating scenario may permit interference to occur between BTSs that are operating on adjacent RF channels.
Present wireless communication systems are not always capable of dealing with such adjacent channel interference. Therefore, it can be appreciated that there is a significant need for an apparatus and method of filtering that enhance operation of wireless communication systems.